The present invention relates to compositions containing heterocyclic compounds having an amide function and having herbicidal activities, to their use in the control and destruction of infestant plants and to the process for preparing them.
It is known that there is a great need in agricolture for new, alternative herbicidal products which have high activities in the elimination of weeds together with a substantial lack of toxicity to man and animals.
According to the present invention these requirements are satisfied by means of new herbicidal compounds having a heterocyclic structure and having an amide group attached to the hetrocyclic structure.
Accordingly the present invention relates to a method for controlling the growth of infestant plants, characterised in that the infested ground is treated with an effective quantity of a herbicidal compound or of a composition containing a herbicidal compound, selected from those which can be defined by the general formula: ##STR3## in which: R is a linear or branched alkyl group containing from 1 to 6 carbon atoms;
the phenyl group; PA2 a phenyl group having a substituent, or several substituents which may be identical or different from each other, selected from the halogens and alkyl (C.sub.1 -C.sub.4), oxyalkyl (C.sub.1 -C.sub.4), halogenoalkyl (C.sub.1 -C.sub.4) and nitro groups; PA2 a linear or branched alkyl group containing from 1 to 12 carbon atoms substituted with one or more halogen atoms; PA2 a cycloalkyl group containing from 3 to 8 carbon atoms; PA2 a (methyleneoxy)alkyl (C.sub.1 -C.sub.5) group; PA2 a (methyleneoxy)phenyl group; PA2 a (methyleneoxy)phenyl group having one or more substituents in the ring which are selected from halogen, (C.sub.1 -C.sub.4) alkyl, (C.sub.1 -C.sub.4) halogenoalkyl groups; PA2 the phenyl group; PA2 the benzyl group; PA2 a phenyl or benzyl group having one or more substituents, which may be identical or different from each other, selected from halogen atoms and (C.sub.1 -C.sub.4) alkyl, (C.sub.1 -C.sub.4) halogenalkyl, (C.sub.1 -C.sub.4) oxyalkyl and nitro groups;
R.sub.1 is a linear or branched alkyl group containing from 1 to 12 carbon atoms; PA1 or R.sub.1 is definable by: ##STR4## where R' is a (C.sub.1 -C.sub.2) alkylene group and R" and R"' are linear or branched alkyl groups containing from 1 to 5 carbon atoms; or R" and R"' taken together with the nitrogen atom to which they are connected form a 5 or 6 membered heterocyclic ring possibly containing another heteroatom selected from O, N and S.
In the definitions above, halogen is intended to mean fluorine, chlorine, bromine or iodine.
Examples of preferred substituents in the general formula (I) given above are:
R=methyl
R.sub.1 =methyl, isopropyl, isobutyl, chloromethyl, cyclobutyl, cyclohexyl, phenyl, chlorophenyl, dichlorophenyl, bromophenyl, fluorophenyl, nitrophenyl, t-butylphenyl and trifluoromethylphenyl.
Specific examples of compounds which fall within the general formula (I) above are:
N-(4-methylfurazan-3-yl)cyclopropanecarboxamide; PA0 N-(4-methylfurazan-3-yl)methylcarboxamide; PA0 N-(4-methylfurazan-3-yl)isopropylcarboxamide; PA0 N-(4-methylfurazan-3-yl)isobutylcarboxamide; PA0 N-(4-methylfurazan-3-yl)benzylcarboxamide; PA0 N-(4-methylfurazan-3-yl)chloromethylcarboxamide; PA0 N-(4-methylfurazan-3-yl)cyclohexanecarboxamide; PA0 N-(4-methylfurazan-3-yl)-2-methylphenylcarboxamide; PA0 N-(4-methylfurazan-3-yl)-4-methylphenylcarboxamide; PA0 N-(4-methylfurazan-3-yl)-4-chlorophenylcarboxamide; PA0 N-(4-methylfurazan-3-yl)-2,4-dichlorophenylcarboxamide; PA0 N-(4-methylfurazan-3-yl)-2-idodophenylcarboxamide; PA0 N-(4-methylfurazan-3-yl)-3-fluorophenylcarboxamide; PA0 N-(4-methylfurazan-3-yl)-3,4-dichlorophenylcarboxamide; PA0 N-(4-methylfurazan-3-yl)-4-tert-butylphenylcarboxamide; PA0 N-(4-methylfurazan-3-yl)-3-trifluoromethylphenylcarboxamide; PA0 N-(4-methylfurazan-3-yl)-2-bromophenylcarboxamide; PA0 N-(4-methylfurazan-3-yl)cyclobutanecarboxamide; PA0 N-(4-methylfurazan-3-yl)-4-nitrophenylcarboxamide; PA0 N-(4-methylfurazan-3-yl)phenylcarboxamide; PA0 N-(4-methylfurazan-3-yl)methylene-oxy-2,4-dichlorophenylcarboxamide.
Some of the compounds represented by the general formula (I) such as those in which R is the methyl group and R.sub.1 is methyl or N-diethyl-methylene-amine or N-methylene-morpholine are known from the literature which describes their synthesis, their physical and chemical characteristics and, in some cases, their pharmacological properties. In this respect one is referred to the following literature:
Il farmaco, Ed Sci. 26, 233 (1971);
Il farmaco, Ed Sci. 32, 789 (1977);
J. Prakt. Chem. 315, 791 (1973);
Swiss Pat. No. 502.365; and
Swisse Pat. No. 508.650.
The present invention is based on the discovery that these known compounds and other new compounds falling within the general formula (I) have herbicidal activities with a wide spectrum of action against infestant plants, but are substantially innocuous to man and animals.
The compounds (I) may be synthesised by the following reaction scheme. ##STR5## In the formulae above, R and R.sub.1 have the meaning indicated previously and X represents a halogen, preferably chlorine.
Typically the basic step of the process of the present invention for preparing the compounds having the general formula (I) is consisting of reacting a 3-amine-(4-R-substituted)-furazan (II) with an acyl chloride R.sub.1 COC1 (III), wherein R and R.sub.1 have the same meaning of the general formula (I), with a (III) to (II) molar ratio of from 1:1 to 1.2:1, at a temperature of from 0.degree. to 100.degree. C., in the presence of a basic compound blocking the halogenic acid, in an inert organic solvent, for a time of from 1 to 10 hours and of recovering the compound (I) from the reaction mixture by filtration. The preferred solvent for the reaction is ethyl ether and the preferred basic compound blocking the halogenic acid is pyridine.
The compounds (I) according to the present invention have good herbicidal activities particularly when used under post-emergence conditions in doses of from 0.1 Kg/hectare up to a maximum of 5 Kg/hectare. Moreover, the herbicidal activity of the compounds (I) is highly selective with regard to crops belonging to the grass family (gramineae) up to doses of 2-2.5 Kg/hectare; at higher doses the herbicidal activity of the compounds tends to become total.
The compounds (I) of the present invention are herbicides which interfere both whith the seed germination phase and with the subsequent development of the embryo plants. They have good herbicidal activities and may thus be used conveniently in post-emergence weed killing in crops, in accordance with the different degrees of selectivity shown and the biological cycles of the infestants.
The compounds (I) of the present invention may be applied by the usual methods, in solution, suspension or emulsion, as powders or as granules, according to the chosen application, as long as the active principle is finely divided.
The compositions of the present invention are typically prepared by the mixture of the active ingredient with an adjuvant including diluents, fillers, extenders and conditioning agents to provide the compositions in the form of finely-divided solid particles, granules, solutions, dispersions or emulsions. The active ingredient may thus be used with an adjuvant such as a finely-divided solid, an organic liquid, water, a wetting agent, a dispersing agent or any suitable combination thereof. The herbicidal compositions of the present invention, particularly liquids or soluble powders, preferably contain one or more surface active agents as conditioning agents in quantities sufficient to render a particular composition readily dispersible in water in oil. The incorporation of a surface active agent in the composition greatly improves its effectiveness. By "surface active agents" are meant wetting agents, dispersing agents, suspensing agents, and emulsifying agents. Anionic, cationic or non-ionic agents may be used equally well.
Preferred wetting agents are alkylbenzene sulphonates, alkylnaphthalene sulphonates, aliphatic alcohol sulphonates, polyoxyethylene derivative of alkylphenols (particularly isooctylphenol and nonylphenol)
Compositions of powders dispersible in water may be made with one or more active ingredients, an inert solid filler and one or more wetting and dispersing agents. The solid inert fillers are usually of mineral origin, for example natural clays, diatomaceous earths and synthetic minerals derived from silica and the like. Examples of such fillers comprise kaolin, attapulgite and synthetic magnesium silicate. The powders of the present invention which are dispersible in water usually contain about 5 to about 95 parts by weight of the active ingredient, from about 0.25 to about 25 parts by weight of the wetting agent, from about 0.25 to about 25 parts by weight of the dispersing agent and from about 4.5 to about 94.5 parts by weight of the solid inert filler, all the parts being with reference to the total weight of the composition.
The aqueous suspensions may be prepared by mixing and grinding together an aqueous suspension of the active ingredient which is insoluble in water to obtain a concentrated suspension of very finely divided particles. The resulting concentrated aqueous suspension has extremely small particles such that when it is diluted and sprayed the coating is very uniform.
The emulsifiable oils are generally solutions of the active ingredient in solvents which are immiscible or slightly miscible with water, together with a surface active agent. Solvents suitable for the active ingredients of the present invention include hydrocarbons and ethers, esters and ketones which are immiscible with water. The composition of the emulsifiable oil generally contains from about 5 to about 95 parts by weight of the active ingredient, from about 1 to about 50 parts by weight of surfactant and from about 4 to about 94 parts by weight of solvent, all the parts being based on the total weight of the emulsifiable oil.